QUESTION $4$

$(20$ marks$)$

A $6\mathrm{.}2$ m high retaining wall, with highly permeable vertical wall back drainage, is retaining and founding on a homogenous Soil. While the main groundwater table is low, during heavy rain, the retained ground is subject to infiltration which results in steady seepage flow. The site condition and the flow net of the steady seepage flow are given in Figure $4.$ The relevant material parameters are as follows:

$\backslash$table$[[$Water$,$Density, ${}_w=10k\frac{N}{m^3}$